In recent years, biometric authentication using biometric information of users is becoming widely used as means for authenticating the users. Examples of available biometric information include capture-image information obtained by capturing images of body parts, such as fingerprints, veins, retina patterns, and voiceprint information obtained by recording voice.
Some biometric authentication apparatuses employing such a method have been proposed.
For example, Japanese Unexamined Patent Application Publication No. 2008-77518 discusses a configuration including means for updating and registering, separately from initially enrolled first reference biometric data, biometric data used each time authentication succeeds, as a second reference biometric data. When the matching rate between the first reference biometric data and the second reference biometric data is lower than or equals to a threshold, a request for re-enrolling the reference biometric data is issued.
In addition, for example, Japanese Unexamined Patent Application Publication No. 2008-79680 discusses a related technology, in which an approximation function expressing aging body parts derived from history of similarity between the enrolled biometric information and sample biometric information for each verifications. When the similarity estimated from the approximation function is lower than or equal to a predetermined threshold, the enrolled biometric information is updated.